Reaction products of an nu-acyl polyimide of a polycarboxylic acid with a polymer containing hydroxy or amino radicals



Patented Apr. 22, 1952 UNITED STATES 2,594,145 PATENT OFFICE REACTIONPRODUCTS OF AN N-ACYL POLY- IMIDE OF A POLYCARBOXYLIC ACID WITH APOLYMER CONTAINING HYDROXY OR AMINO RADICALS Paul J. Flory, Ithaca, N.Y,., assignor to Wingfoot Corporation, Akron, Ohio, a corporation ofDelaware No Drawing. Application April 29, 1950,, Serial No. 159,153

1 This invention relates to the preparation of polymers and moreparticularly to the preparation of polymers of high molecular weight bycoupling or interlinking polymers of lower molecular weight by means ofa particular type of '5 interlinking agent.

In many instances, while it is relatively easy to prepare polymers ofmoderate molecular weight, it is much more diflicult to prepare polymersof high molecular weight. Thus, in pre- 10 HO-R-OH i 13 Claims. ,(Cl.260-75) paring superpolyamides or superpolyesters, and particularly inthe latter case, it is often difficult to carry the reaction tocompletion. Thus, polymers of sufficiently high molecular weight to havethe desired properties, for example, for the production of fibers,plastics, films, etc., cannot easily be prepared.

One object of the present invention is to facilitate the production ofpolyamides, polyesters and polyesteramides of high molecular weight moreefficiently and in shorter times than by other available means. Anotherobject of the invention is to facilitate the preparation of suchpolymers in instances where the preparation is diflicult by other means.Another object is to prepare such polymers without producing undesiredside reactions and degradation which attend some of the previouslyavailable methods. Other objects and advantages will appear as thedescription proceeds.

According to the practice of the invention, a polymer having a pluralityof hydroxyl and/or amino radicals attached thereto is treated with anN-acyl polyimide of a polycarboxylic acid, in which each of the carbonylgroups of the acyl radical is attached to the nitrogen atom of an imidoradical. The amino radicals in the polymers must contain at least onereactive hydrogen and are preferably primary amino. The N-acyl o o o v o1 no-a-o-tL- cal)Pt IL-Q-O- -K O O -CH: CHr- The mechanism of thereaction is not known for certain and it is possible that both of theindicated types of reaction occur. It appears that the reaction takesplace at least in part according to equation (A) since some free imideis formed and can be recovered and identified.

In the equations, reaction has been shown on only one end of each of thestarting materials. Similar reaction can and, in practice, does takeplace on both ends of the molecules.

A particularly important and valuable application of the invention is inthe production 01 linear polymers of high molecular weight. For example,it is frequently difficult to obtain linear polyesters (of theglycol-dicarboxylic acid type) having molecular weights sufiicientlyhigh for optimum physical properties. Direct esterification ofdicarboxylic acid and glycol proceeds slowly, particularly when themolecular weight becomes moderately large. Reaction of the glycol with adicarboxylic acid chloride is much faster but is inapplicable to certaintypes and in other cases it may be preferred to avoid use of the acidchloride because of unavailability or because of the deleterious effectsof the hydrogen chloride released during the reaction; According to thepresent invention, a polyester or ,polyamide or polyester-amide of lowor moderglycol used :in excess of the sebacyl chloride.

amino end-groups can be converted within a" relatively short period oftime to a polymer of high molecular weight.

Various methods are available for preparing low polymers withterminal-.hydroxyl. and/or, amino end groups. For examplaa .dicarboxylicacid can be reacted with more than an equivalent proportion of glycoland/or diamine. Small exce'sses produce larger polymer :moleculeswhilelarge excesses produce smaller molecules. Polyamides can also beprepared by reacting a dicarboxylic acid chloride with anexcessofildiamine. Some polyesters can also be prepared byreacting anexcess of glycol with an acid chloride. Polyamides can also be preparedby self-polymerization of a monoamino-monocarboxylic acid the presenceof a" diamine. Polyesters" canbe prepared similarly from amonohydroxymonocarboxylic "acid" and" a glycol. ---Polyes.t'ers can beprepared by an ester interchange reaction between a'glycol andan 'alkylor aryl ester of a dicarboxylicacid. The particular method for "formingthe terminalaminoand/or hydroxyl groups is not part f the presentinvention, which is directed intermediate polymer having to theinterlinking of such polymers, however formed.

In order to produce polymers of very high molecular weight-the.molecular quantities of interlinking agent and initial polymerenteringinto the reactionrmust be approximately equal. One way of ensuring thisis to mix them in the proper proportion. --Another -way is to add "theinterlinking agent portionwise, with complete reaction before thenextaddition.

The practice of lthe invention in the preparation of linear polymers isillustrated by Examples 1 to 6.

Example 1 Seventeen grams of sebacyl chloride and 13.0 grams. (5 molpercent excess) of decamethylene gly col werependensedbyheating themtogether in a, glass tube at 110 C. for three hours and then at'175 C.for two hours. Inert gas (pure nitrogen) was bubbled through the polymerto sweep .izoutievolved hydrogen chloride and to avoidall icontaminationwith air. The meltviscosity oi zthe. resulting low molecular weight,hydroxyl groupterminated, decamethylene sebacate poly- :"esterwwas 11.5.poises at 200 C. The viscosity showed: little .change .with furtherheating. The

FnumberaVerage molecular weight estimated from athe, melt viscosity (seeJ. Am. Chem. Soc. 62, 1057 11940)) is 6700, a value in; approximateagreement with that expected from the amount of To 6.13 grams of theabove polyester was added 0.439

c grams? of N,N'sebacyl-bis-phthalimide, representing a small excessover the amount required The mixture was" then heated Time oi heating at200 0., in minutes .The molecular *weight estimated from the finalviscosity is 23,000. Whereas the polymer prior 1 *to interlinking wasrelatively friable and of low --strength, the higher polymer obtainedthrough Fiber from the out drafting. Fibers from the final polymercould'be cold-drawn'in a manner characteristic of A poises.

crystalline linear. high polymers, and the cold drawn fibers exhibitedhigh tenacities.

Example 2 'ninety-hundredths grams of thispolymer and 0.20 grams ofN',N-sebacyl bis-succinimide were heated at 175 C. as described above.Within170 minutes, the viscosity had risen. to 1,680 poises.

After. heating for 160. minutes, the viscosity was 5,100 poises. andafter 2301'minutesit'was6,950 The final. viscosity corresponded'to a 7number average weight of approximately 21,500.

The product was tough and strong and fibers formed from it could be colddrafted readily.

Erample 3 Fifteen-hundredths grams of N,Nisophtha1- oyl-bis-succinimidewas added to 3.00 grams of the low molecular weight decamethylenesebacate polyester used in Example 2, and the mixture was heated at 200C. for 90 minutes. The viscosity of the-melt was 5,200 poises. Afterheating for an additional four hours, it was 13,000 poises.

Example 4 .A slow stream of dry,.oXygen.-free nitrogenwas passed throughthe melt while heating for'about an hour at this temperature. The meltviscosity was 283 poises at 241 C.,.and showedrelatively little changewith further heating. Four hundred fifty-six thousandths grams of N,N'-sebacylbis-phthalimide was added to 8.79 grams of the above polymerand the mixture Was heated in the usual mannerat 241 C. After 90minutesthe viscosity reached 1,680 poises. An additional 0.076 gram of IT,N-sebacyl-bis-phthalimide was added to the mixture, which was thenheated for an additional half hour. The finalviscosity was 2,600 poises.I Whereas: the molecular weight of the initial polyme was too low'formanifestation of good fiber properties,thefinal polymerswas well withinthe desiredmolecular weight range,

fibers from the latter polymer readily-cold drafting to yield welloriented fibers exhibiting high tenacity.

Example 5 p A low molecular weight ethylene terephthalate was preparedby reacting dimethyl terephthalate with. excessethylene glycol in thepresence 10f catalytic amounts 'of magnesium ribbon at refluxtemperatures. The excess glycol was removed in vacuo and the polymer washeated in vacuo at 280 C. until the melt viscosity at this temperaturewas 25 poises. This polymer has an estimated molecular weight of 5,760.To milliliters of o-dichlorobenzene in an all-glass polymerization tubewas added 4.342 grams of the polymer and the mixture was heated atreflux until solution was complete. To this solution was added 0.34?gram of N,N-sebacyl diphthalimide and the solution was heated at refluxfor 2.5 hours. The solvent was distilled off and the thick viscouspolymer had a melt viscosity of 5,200 poises at 280 C. The polymer was alight tan, crystalline solid with a melting point of 261-263 C.

Example 6 A low molecular weight polyamide having amino end groups wasprepared by reacting decamethylene diammonium sebacate (the simple saltof equimolecular proportions of decamethylene diamine and sebacic acid)with 7 mol percent (based on the decamethylene diammonium sebacate) ofdecamethylene diamine, the reaction being carried out at 218 C. for twohours. The resulting polymer had a melt viscosity of 74.8 poises at thistemperature. Three and three hundred twenty-eight thousandths grams ofthis polymer were reacted with 0.345 gram, ofN,N'-sebacylbis-phthalimide by thoroughly mixing the two solid reactantsand heating them under nitrogen for one hour at 218 C. The clear moltenpolymer had a final melt viscosity of 1,624 poises at 218 C. Itcrystallized, on cooling, to a creamy-white solid. The melting point ofboth the low viscosity polymer and the final product was l-203 C. Fibersprepared from the final product were cold drawable.

Cross-linked polymers having properties simi-' lar to those of avulcanized rubber or a gelled or thermoset resin can be prepared by theprocess of the invention when either or both the N-acyl polyimide andthe intermediate" polymer contain more than two functional groups.

For example, such products result when a linear. polyester or polyamideor polyesteramide having hydroxyl and/or amino end groups is treatedwith an N-acyl polyimido compound having three or more imido groups permolecule.

Another method for preparing cross-linked or network polymers is byreacting a nonlinear polyester, polyamide or polyesteramide containingmore than two amino and/or hydroxyl groups per molecule with an N-acylpolyimide containing at least two imido groups per molecule. Suitablenonlinear polymers may be prepared, for example, by condensing a glycol,dibasic acid and a polycarboxylic acid having a functionality greaterthan two or by condensing a glycol, a polyhydric alcohol having afunctionality greater than two and a dicarboxylic acid. In preparingthese initial polymers, it is preferred to use a sufficient amount ofglycol to prevent gelation of the composition of the esterificationprocess or, if gelation does occur, the condensation preferably shouldnot proceed to an extent beyond the gelation point such that the productcannot be milled or molded or otherwise processed in the subsequentinterlinking reaction. The proportion of the glycol required for a givenamount of the polyfunctional compound may be determined by trial or itmay be computed approximately from theory. (See JACS, volume 63, page3083 (1941) Further examples of suitable polymers having a functionalitygreater than two are those of the multichain type prepared by reacting arelatively small amount of an alcohol containing at least three reactivehydroxyl groups with a relatively large amount of a monohydroxymonocarboxylic acid or by reacting a relatively small amount of apolyamino compound containing at least three reactive amino groups witha relatively large amount of a monoaminomonocarboxylic acid or amonohydroxymonocarboxylic acid. The nonlinear polymer prepared accordingto one of these methods, or any other method, is then treated with apolyimido compound having a functionality of at least two. It ispreferred to use a proportion of this compound which is approximatelyequivalent to the hydroxyl or amino groups present in the polymer. Thispolyimido compound is incorporated by stirring, milling or by dissolvingin a suitable solvent. This mixture can be molded or cast into the formof the final object and reaction effected by heating at elevatedtemperature.

Also included in the scope of this invention is rivatives thereof whichcontain free hydroxyl groups may be similarly treated.

The polyimido compound is preferably used in an amount approximately instoichiometric equivalence with the hydroxyl and/ or amino end groups.

Thus, the invention includes the conversion or thermoplastic polymershaving at least two hydroxyl and/or amino groups per molecule tovulcanized or thermoset compositions through treatment with polyimidocompounds as described above, If the initial polymer molecules containonly two hydroxyl and/or amino groups per molecule, as in the case oflinear polymers terminated with hydroxyl and/or amino groups, apolyimido compound containing a least three imido groups must be used inorder to achieve cross-linking. If the number of available hydroxyl and/or amino groups per molecule is three or greater, either the bisorhigher polyimido compounds may be used.

The practice of the invention in preparing cross-linked polymers isillustrated by the following representative examples.

Example 7 Fifteen and seventy-eight hundredths grams (0.156 equivalent)of isophthalyl chloride and 1.37 grams (0.015 equivalent) ofcyclohexanone tetrapropionic acid were heated cautiously ina flask untilevolution of hydrogen chloride subsided. Seventeen and forty-threehundredths grams (0.200 equivalent) of decamethylene glycol and 50 cubiccentimeters of ethylene chloride were added and the mixture was refluxedfor 18 hours, after which the solution was transferred to a cylindricalreaction tube 32 millimeters in diameter and of the type ordinarily usedfor polyesterifications. Solvent was removed. by distillation throughthe side arm above the reaction tube assembly, a stream of nitrogenbeing passed through the polymer. The molten polymer was quite fluid.The interlinking agent (6.81 grams or 0.030 equivalent ofN,N-sebaeyl-bis--phthal- -an produ t .w s-;rubbery;atgroo temperature;It

P'fimide)....,was;; then-ratifie an -thez.-:.m x.iu y

a C. .esm xtu c th ck. nee-rap d y aseomplet yi-eell wi hin; e .heu The-underwent:sire linainac loroform b t wou d a iesolve. rc mplet lr. in:zih s s l en h .inert solvents.

- Example 8 Seventeen -andninety-one hundredths. grams .1165 equivalent).0: isophthalyl-chloride and 17.43 grams-.40.:20OQ equivalent) of.decamethyl- ,ene glycol-wereplaced in a cylindrical reaction tube32rnillimeters .in diameter, together with -eu cc n imete s: -dichl ro ce i vpurenitrogen louhhling through the mixture, theygwereallowed;toreact sit- 61 C; for one and "ahalhhcursand-atn eflux for 7hours asolvent was.themdistilled-ofi, thepolymer was cooled andQ.756,grams.:(0.-0078. equivalent) of cyclohegranone tetrapropionicacid. was added. The mixture was heated at 218 C:.-Nith pure nitrogenbubbling through the melt for nine hours. The

., viseo ity .was about,21 poises at thistemperature.

{lThe interlinking agent .(2.80 grams or 0.0122

. 1 A .,.,.method for. increasing the. molecular lweig'ht of polymercontaining at leasttwo radicals selected from thev group. consisting of,hydrcxyl radicals. and amino radicals. containingyatlea-stone reactivehydrogen .atom which -co nprise.s...,heat-ine.. i po ymer. w h a N-e yl.nc yim eoi a p l a b xr i in wh c .eac

..i ..t e .c rbgn l. eens. he, .acyl adi -l s tached tothenitrogenatomof an irnido radical. in tho i crea i t ol cul we ht. p m con ai a leatwo radica s. l ct d-hem t e. ro consist n 0f .hydre l radic s d am oradic on a .insat. ea t o ei'eeei hy n ie wh om ris sheat n sa d Pol mwi .N-a

polyimide oi. a polycarboxylic acid in which each of' the carbonylgroups, off the, acyl radical is atechedtmt en t qe n ato o n mi o r i.ee q' tN-a l o r mid .bei s amo equivalentto said hydroxyl and aminoradicals.

3. A method for increasing the molecular weight of a polymer-containingat least two radicals selected from the group consisting ofhyd-roxyl-radicals and amino radicals containing-atleast one reactivehydrogen atom'which ---co mp rises heating said polymer with an N,N-ecyi-bis-i ide of a-dicarboxylic acid, said N.N'-

ac lrlq mi bei g us d-in a ou t equivale to. said. hydrpxyl v and amino.radicals.

4....A method; for increasing the molecular weight of a polymercontaining. tworadicalsselected from the. group consisting othydroiiylradicals and amino radicals containing at least one reactive hydrogenatom which cornprises heating said polymer with. an N,N'-acyl- -hisimideof a dicarboxylic acid, said v N,N'- acyl l)isimide being used in amountequivalenato said hydroxyl and amino radicals.

5. A- method for increasing the mg1e cu lar 4 weight of a polymercontaining atleast, two hydroxyl radicals which comprises heating. feaidpolymer with an N-acyl polyimideofia'polycarboxylic acid in which eachof the carbonyl jgroups of the acyl radical is attached to the nitrogenatom of an imido radical.

, 6. A method .for; increasing the molecular weight of a linearpolyester containing. terminal a hydroxyl .radicals which comprisesheatingsaid polymer with. an. N,N,-acyl-bis-imide. ofl al dicarboxylicacid.

7. A- method forweight of polymeric tetramethylene terephthalate.containing terminal hydroxylradicals which comprises heating saidpolymer with an'N,N-

V acyl-bis-imide of a dicarboxylicacid.

8. A method for preparing a superpolymer which comprises heatingequivalent proportions of N,N -sebacyl-bismhthalimide and polymerictetramethylene terephthalate having. terminal hydroxyl groups.

9. A method for. increasing the mo lecular weight of a polymercontaining at least two amino radicals. which, comprises heating saidpolymer w anNz c l o mi e of mammboxylic acid in whicheach oi thecarhonyljg'rcups .of. the acyl .radical is. attached to the nitroge atomof an imidoradical.

10. .A .method for increasin the molecular ,weight of polymeric ethyleneterepl thalate eontainingterminal hydroxyl radicals which comprisesheating said polymer with an N;Nf.- -acy1- bis-imide of a dicarloo gylicacid.

11. A method for increasing the molecular weight of cellulose. whichcomprises heating the cellulose with an N,N' -acyl-bis-imide of adicarboxylic acid.

12. A method for increasing the molecular weight of a vinyl alcoholpolymer containing multiple hydroxyl 7 groups which comprises heatingsaid polymer with an N-acyl polyimide of a polycarboxylic acid. in whicheach of the carbony] groups of the'acyl radical isattached-to thenitrogen atom of an ilnido radical.

13. A method ior increasing the molecular weight of polyvinyl alcoholwhich comprises heating the polyvinyl alcohol with anN,-N'-acylbis-imide of a dicarboxylic acid. PAUL J; FLORY.

: o. ref r nc s cit increasing the .molecular V

1. A METHOD FOR INCREASING THE MOLECULAR WEIGHT OF A POLYMER CONTAININGAT LEAST TWO RADICALS SELECTED FROM THE GROUP CONSISTING OF HYDROXYLRADICALS AND AMINO RADICALS CONTAINING AT LEAST ONE REACTIVE HYDROGENATOM WHICH COMPRISES HEATING SAID POLYMER WITH AN N-ACYL POLYIMIDE OFAPOLYCARBOXYLIC ACID IN WHICH EACH OF THE CARBONYL GROUPS OF THE ACYLRADICAL IS ATTACHED TO THE NITROGEN ATOM OF AN IMIDO RADICAL.